Known as a conventional laser processing method is one irradiating a planar object to be processed with laser light while using one face of the object as a laser light entrance surface, so as to form a plurality of rows of modified regions to become a cutting start point within the object such that the modified regions align in a thickness direction of the object, wherein the modified region closest to the other face is exposed at the other face (see, for example, Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open No. 2005-123329